Technical Field
This invention relates to a signal processing circuit and a signal processing method that are suitable to be used together with a capacitive position detecting sensor, which allows detection of the respective indicated positions by plural indicators such as fingers (multipoint detection), and a position detecting device and electronic apparatus incorporating such circuit and method.
Description of the Related Art
Position detecting devices such as a touch panel have come to be widely used and various inventions relating to the position detecting devices have been made. For example, Japanese Patent Laid-open No. 2011-243081 (Patent Document 1) discloses an invention relating to a capacitive touch panel device. In the invention disclosed in Patent Document 1, plural transmitting electrodes 2 and plural receiving conductors 3 are disposed in a lattice manner to form a panel main body 4 and predetermined signals are supplied to the transmitting electrodes 2. At a position indicated by a finger as an indicator, a current is shunted via the finger. Due to this, capacitance formed between the transmitting electrode 2 and the receiving conductor 3 changes. This capacitance change is detected as the change in the current flowing in the receiving conductor 3.
Therefore, the position indicated by the indicator on the panel main body 4 can be detected by detecting the current change at the respective intersections of the transmitting electrodes 2 and the receiving conductors 3. However, the current that changes in the receiving conductor 3 is weak. Thus, the weak current is converted to a voltage of a proper signal level and then processed. Also in the above-described Patent Document 1, it is explained that a weak current flowing in the receiving conductor 3 is converted to a voltage to be processed by using an I-V converter (current-voltage converter) 31 using an operational amplifier OPA.